1. Field of the Invention
The invention relates to a water stop sheet for a wiring harness and a water stop structure of a wiring harness to prevent water from entering a vehicle interior along a wiring harness that passes through a hole of a panel between a water susceptible area, such as an engine room, and the vehicle interior of a vehicle.
2. Description of the Related Art
The Publication of Japanese Patent No. 3417324 discloses a water stop structure for a wiring harness that passes through a grommet and is mounted in a through hole of a vehicle body panel. A water stop agent, such as silicone resin, is filled between parts of the wires of the wiring harness inserted through the grommet for stopping inter-wire water.
The above-described water stop structure prevents water from entering from into a vehicle interior, but requires many difficult manual operations and dedicated tools, which leads to a cost increase. Further, a visual inspection cannot be carried out since water is stopped in the grommet, and a water-stop inspection requires immersion in water, such as in a water tank. This inspection increases costs. Further, a silicone resin filling of an inter-wire water stop portion becomes hard after curing and can peel when bent, thereby destroying the inter-wire water stopping.
The subject inventor discloses a water stop method in the Publication of Japanese Patent No. 3692969 that differs from the above-described water stop technique. This alternate water stop method winds a waterproofing closed cell foamed sheet 120 around a wiring harness 100 and fits this assembly through a grommet 110 that is to be mounted into a through hole of a vehicle body panel. The waterproofing foamed sheet 120 closely contacts the inner peripheral surface of a small-diameter tube portion 110a of the grommet 110 to prevent the entrance of water from a water susceptible area of an engine room into a vehicle interior, as shown in FIGS. 5 and 6(A) to 6(C).
Specifically, the closed cell foamed sheet 120 has adhesive layers 121, 122 on both sides. As shown in FIG. 6(A), wires 100w of the wiring harness are arranged at intervals in a half area of the adhesive layer on the top side of the foamed sheet 120, and the remaining half is folded to sandwich the wires 100w between upper and lower parts of the adhesive layer 121 on the top side, as shown in FIG. 6(B). The foamed sheet 120 folded in two then is wound to adhere parts of the adhesive layer 122 on the under side as shown in FIG. 6(C). The small-diameter tube portion 110a of the grommet 110 shown in FIG. 5 is expanded by a tool, and a part of the wiring harness 100 wound with the foamed sheet 120 is inserted and resiliently compressed in the small-diameter tube portion 110 to be fixed in the grommet 110.
The adhesive layers on the inner and outer peripheral surfaces of the wound foamed sheet 120 are overlapped and fixed to block the entrance of water. Further, the closed cell foamed sheet 120 can block the entrance of water in a direction perpendicular to the axial direction from the outer peripheral surface into the interior during car washing and high-pressure washing.
Folding the foamed sheet 120 to sandwich the wires 100w and then winding the assembly at least one turn enlarges the diameter of the water stop part. This large diameter water stop part must be pushed into the small-diameter tube portion 110a of the grommet 110 by expanding the small-diameter tube portion 110a using the tool, and an operation of inserting the wiring harness 100 with the water stop part into the grommet 110 requires much trouble. In addition, the small-diameter tube portion 110a of the grommet 110 is not easily curved due to the enlarged in diameter of the water stop part. Thus, the wiring harness is not bent easily by 90° to lie along the vehicle body panel immediately after inserting the wiring harness through the through hole of the vehicle body panel.
Further, the adhesive layers extend across all of both surfaces of the foamed sheet. The foamed sheet may be creased during the folding, adhering and winding, and the foamed sheet is adhered in a creased state. Once adhered, the adhesive layers are not easily peeled. Thus, adhering and winding the foamed sheet in a crease-free state is difficult. A clearance formed in a creased part of the sheet serves as a water entrance path and the reliability of water stop performance is reduced.
An adhesive layer that is provided only on the top side of a foamed sheet could be peeled easily during an operation of folding, adhering and winding. Thus, the operations easily can be redone if the foamed sheet is creased. However, this approach reduces an adhesive force at a winding end and the foamed sheet tends to be peeled from the winding end.
In view of the above problems, an object of the invention is to provide a water stop sheet that is unlikely to be creased when being wound around a wire group of a wiring harness, and enables an operation to be redone easily even if the water stop sheet is creased and is unlikely to be peeled from a winding end. Another object of the invention is to provide a water stop structure of a wiring harness that uses the water stop sheet, requires no dedicated tool, has good operability and can be formed without increasing cost.